An automatic swing door is installed to close and open a doorway, and is rotatable about a rotation axis disposed along one side of the doorway. When a moving object, e.g. a human, enters into a sensing zone for opening the door formed on one side or "approach-side" of the door, the door is driven to swing in the direction toward the other side or "swing-side" of the door. After the moving object passes the doorway, the door is rotated toward the approach-side to thereby close the doorway. If there is an object in the path of the door either on the swing-side or the approach-side, it may collide with the swing door. In order to prevent it, a sensor is disposed on each of the approach-side and the swing-side of the swing door, so that a sensing zone for safety is formed on both sides of the door. If any object is in the sensing zone, the rotation of the door may be stopped, decelerated, or reversed to prevent the door from damaging the object.
A sensor for this purpose is disclosed in, for example, U.S. Pat. No. 4,560,912, which is an aerial radiation type. The sensor of U.S. Pat. No. 4,560,912 uses a light-emitting device and a light-receiving device which establish sensing zones extending from the swing door into the air. German Patent No. 4,415,401 discloses a plurality of sensors disposed above a swing door. Each sensor has a light-emitter and a light-receiver, so that a plurality of sensing zones extending between the sensors and the floor are formed.
Guardrails may be installed near the path of the swing door. The system disclosed in German Patent No. 4,415,401 can detect small objects on or near the floor, but it may also detect the guardrails, so that the swing door may be unnecessarily stopped in response to detection of the guardrails. Therefore it is desirable that no irrelevant objects be sensed, in order to ensure the stable door operation.
Further, it is desirable that when a moving object as well as a guardrail come to enter into a sensing zone, only the moving object be detected, and the guardrail be not detected, so that the door is not stopped in response to detection of the guardrail, and, therefore, the moving object can pass through the doorway swiftly. According to the technology disclosed in U.S. Pat. No. 4,560,912, the position of the sensing zones may be properly determined in such a manner as to prevent the sensing of the guardrail by the sensor, which could undesirably stop the swing door. However, the system of U.S. Pat. No. 4,560,912 sometimes cannot detect a small object, e.g. an infant, on or near the floor. It is, therefore, desired to provide a sensing system which does not detect irrelevant objects but detects only relevant objects.
Swing doors may be installed in a variety of environments. Accordingly, in order to ensure proper operation of a swing door, the amount of light emitted by light-emitters of a sensor and the amount of light received by light-receivers must be adjusted to values suitable for the environment in which the swing door is installed. It is desirable that such adjustment be done automatically.
The environmental condition in which a door is installed may vary with time. It is also desired that the sensor be adjusted automatically with changes in the environment.
The speed of the door when it rotates is higher at the distal edge of the door remote from rotation center than at portions nearer to the rotation center. Accordingly, if an object collides with the distal edge of the door, the object may be damaged severely. Therefore, it is desired that an object in the sensing zone adjacent to the distal edge of the door be sensed without fail.
An object of the present invention is to ensure stable operation of an automatic swing door.
Another object of the present invention is to provide a system which senses only a moving object.
Still another object of the present invention is to make a sensing zone adapt itself to difference and changes in environment where the automatic swing door is installed.
A further object of the present invention is to improve the sensing precision in a sensing zone near the swing door portion which moves at a high speed.